Corneal lymphangiogenesis facilitates ocular surface inflammation and cell trafficking in dry eye disease

While the normal cornea has limited innervation by the lymphatic system, chronic immune-inflammatory disorders such as dry eye (DE) can induce lymphangiogenesis in the ocular surface. Using a conditional knock-down murine model, Lyve-1^Cre;VEGFR2^flox mice, this study investigated the role of lymphangiogenesis in the pathophysiology of DE.

DE was induced in both wild type (WT) B6 and Lyve-1^Cre;VEGFR2^flox mice. Tissue immunostaining and volumetric gross measurements were used to assess changes in the ocular surface, skin, and lymph nodes (LNs). The expression of lymphangiogenic factors (TNF-α, IL-6/-8/-12/-17, VEGF-C/-D, IFN-γ, VEGFR-2/-3, Lyve-1, and podoplanin) and the frequency of immune cells (CD4, CD11b, and CD207) on the ocular surface and lacrimal glands were quantified by real-time polymerase chain reaction and flow cytometry.

Compared to WT mice, there were fewer lymphatic vessels and a reduction in lymphangiogenic markers in the ocular surface and skin of Lyve-1^Cre;VEGFR2^flox mice. After DE induction, mRNA levels of TNF-α, IL-8, and IFN-γ were significantly reduced in Lyve-1^Cre;VEGFR2^flox mice compared to WT mice (p < .01). Surprisingly, the LNs from Lyve-1^Cre;VEGFR2^flox mice with DE were significantly smaller and populated by fewer dendritic cells and effector T cells than those from WT mice (p < .001). Furthermore, immunostaining showed corneal nerves in the DE-induced Lyve-1^Cre;VEGFR2^flox mice were notably intact like in the naïve condition.

Inhibition of lymphangiogenesis in the cornea effectively attenuates not only the inflammatory response including trafficking of immune cells but also preserves corneal nerves under desiccating stress. Corneal lymphangiogenesis might be a contributing factor in deterioration on the ocular surface homeostasis.